xref: /dragonfly/lib/libc/sys/chroot.2 (revision a361ab31) 
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28.\"     @(#)chroot.2	8.1 (Berkeley) 6/4/93
29.\" $FreeBSD: src/lib/libc/sys/chroot.2,v 1.7.2.8 2002/12/11 14:06:37 ru Exp $
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31.Dd August 1, 2010
32.Dt CHROOT 2
33.Os
34.Sh NAME
35.Nm chroot ,
36.Nm chroot_kernel
37.Nd change root directory
38.Sh LIBRARY
39.Lb libc
40.Sh SYNOPSIS
41.In unistd.h
42.Ft int
43.Fn chroot "const char *dirname"
44.Ft int
45.Fn chroot_kernel "const char *dirname"
46.Sh DESCRIPTION
47.Fa Dirname
48is the address of the pathname of a directory, terminated by an ASCII NUL.
49.Fn Chroot
50causes
51.Fa dirname
52to become the root directory,
53that is, the starting point for path searches of pathnames
54beginning with
55.Ql / .
56.Pp
57In order for a directory to become the root directory
58a process must have execute (search) access for that directory.
59.Pp
60It should be noted that
61.Fn chroot
62has no effect on the process's current directory.
63.Pp
64This call is restricted to the super-user.
65.Pp
66Depending on the setting of the
67.Va kern.chroot_allow_open_directories
68sysctl variable, open filedescriptors which reference directories
69will make the
70.Fn chroot
71fail as follows:
72.Pp
73If
74.Va kern.chroot_allow_open_directories
75is set to zero,
76.Fn chroot
77will always fail with
78.Er EPERM
79if there are any directories open.
80.Pp
81If
82.Va kern.chroot_allow_open_directories
83is set to one (the default),
84.Fn chroot
85will fail with
86.Er EPERM
87if there are any directories open and the
88process is already subject to a
89.Fn chroot
90call.
91.Pp
92Any other value for
93.Va kern.chroot_allow_open_directories
94will bypass the check for open directories
95.Pp
96Upon successful completion, a value of 0 is returned.  Otherwise,
97a value of -1 is returned and
98.Va errno
99is set to indicate an error.
100.Pp
101The
102.Fn chroot_kernel
103system call adjusts the kernel's internal namecache and root vnode
104references to
105.Fa dirname .
106If used in conjunction with
107.Fn chroot
108during early boot, it allows for changing the root mount to any
109mount point available at that time.
110.Sh ERRORS
111.Fn Chroot
112will fail and the root directory will be unchanged if:
113.Bl -tag -width Er
114.It Bq Er ENOTDIR
115A component of the path name is not a directory.
116.It Bq Er EPERM
117The effective user ID is not the super-user, or one or more
118filedescriptors are open directories.
119.It Bq Er ENAMETOOLONG
120A component of a pathname exceeded 255 characters,
121or an entire path name exceeded 1023 characters.
122.It Bq Er ENOENT
123The named directory does not exist.
124.It Bq Er EACCES
125Search permission is denied for any component of the path name.
126.It Bq Er ELOOP
127Too many symbolic links were encountered in translating the pathname.
128.It Bq Er EFAULT
129.Fa dirname
130points outside the process's allocated address space.
131.It Bq Er EIO
132An I/O error occurred while reading from or writing to the file system.
133.El
134.Sh SEE ALSO
135.Xr chdir 2 ,
136.Xr jail 2
137.Sh HISTORY
138The
139.Fn chroot
140function call appeared in
141.Bx 4.2 .
142